深度学习之 mnist 手写数字识别

深度学习之 mnist 手写数字识别

开始学习深度学习，先来一个手写数字的程序

import numpy as np
import os
import codecs
import torch
from PIL import Image

lr = 0.01
momentum = 0.5
epochs = 10

def get_int(b):
    return int(codecs.encode(b, 'hex'), 16)

def read_label_file(path):
    with open(path, 'rb') as f:
        data = f.read()
        assert get_int(data[:4]) == 2049
        length = get_int(data[4:8])
        parsed = np.frombuffer(data, dtype=np.uint8, offset=8)
        return torch.from_numpy(parsed).view(length).long()

def read_image_file(path):
    with open(path, 'rb') as f:
        data = f.read()
        assert get_int(data[:4]) == 2051
        length = get_int(data[4:8])
        num_rows = get_int(data[8:12])
        num_cols = get_int(data[12:16])
        images = []
        parsed = np.frombuffer(data, dtype=np.uint8, offset=16)
        return torch.from_numpy(parsed).view(length, num_rows, num_cols)

def loadmnist(path, kind='train'):
    labels_path = os.path.join(path, 'mnist' ,'%s-labels.idx1-ubyte' % kind)
    images_path = os.path.join(path,'mnist' ,'%s-images.idx3-ubyte' % kind)
    
    labels = read_label_file(labels_path)
    images = read_image_file(images_path)
    return images, labels

import torch.utils.data as data
import torchvision.transforms as transforms

class Loader(data.Dataset):
    def __init__(self, root, label, transforms):
        self.imgs = []
        
        imgs,labels = loadmnist(root, label)
        
        self.imgs = imgs
        self.labels = labels

        self.transforms = transforms
        
    def __getitem__(self, index):
        img, label = self.imgs[index],self.labels[index]
        
        img = Image.fromarray(img.numpy(), mode='L')
        if self.transforms:
            img = self.transforms(img)
        
        return img, label
    
    def __len__(self):
        return len(self.imgs)

def getTrainDataset():
    return Loader('d:\\work\\yoho\\dl\\dl-study\\chapter0\\', 'train', transforms.Compose([
        transforms.ToTensor(),
        transforms.Normalize((0.1307,), (0.3081,)),
    ]))

def getTestDataset():
    return  Loader('d:\\work\\yoho\\dl\\dl-study\\chapter0\\', 't10k', transforms.Compose([
        transforms.ToTensor(),
        transforms.Normalize((0.1307,), (0.3081,)),
    ]))

import torch as t
import torch.nn as nn

class Net(nn.Module):
    def __init__(self):
        super(Net, self).__init__()
        self.features = nn.Sequential(
            nn.Conv2d(1, 10, kernel_size=5),
            nn.MaxPool2d(2),
            nn.ReLU(inplace=True),
            nn.Conv2d(10, 20, kernel_size=5),
            nn.Dropout2d(),
            nn.MaxPool2d(2),
            nn.ReLU(inplace=True),
        )
        
        self.classifier = nn.Sequential(
            nn.Linear(320, 50),
            nn.ReLU(inplace=True),
            nn.Dropout(),
            nn.Linear(50, 10),
            nn.LogSoftmax(dim=1)
        )
    
    def forward(self, x):
        x = self.features(x)
        x = x.view(x.size(0), -1)
        x = self.classifier(x)
        
        return x

net = Net()

import torch.optim as optim
from torch.nn.modules import loss

optimizer = optim.SGD(net.parameters(), lr=lr, momentum=momentum)
criterion = loss.CrossEntropyLoss()

train_dataset = getTrainDataset()
test_dataset = getTestDataset()

train_loader = torch.utils.data.DataLoader(train_dataset, batch_size=4, shuffle=True)
test_loader = torch.utils.data.DataLoader(test_dataset, batch_size=4, shuffle=False)

from torch.autograd import Variable as V

def train(epoch):
    for i, (inputs, labels) in enumerate(train_loader):
        inputs_var, labels_var = V(inputs), V(labels)
        
        outputs = net(inputs_var)
        losses = criterion(outputs, labels_var)
        
        optimizer.zero_grad()
        losses.backward()
        optimizer.step()
        
def test(epoch):
    for i, (inputs, labels) in enumerate(test_loader):
        inputs_var = V(inputs)
        
        outputs = net(inputs_var)
        
        _, pred = outputs.data.topk(5, 1, True, True)
        
        batch_size = labels.size(0)
        pred = pred.t()
        corrent = pred.eq(labels.view(1, -1).expand_as(pred))
        
        res = []
        for k in (1,5):
            correct_k = corrent[:k].view(-1).float().sum(0, keepdim=True)
            res.append(correct_k.mul_(100.0 / batch_size))
        print('{} {} top1 {} top5 {}'.format(epoch, i ,res[0][0], res[1][0]))

def main():
    for epoch in range(0, epochs):
        train(epoch)
        test(epoch)

main()

学习之后的，正确率很高，这种问题对于深度学习已经解决了。